In several communications systems the data to be transmitted is compressed so that the available bandwidth is used more efficiently. For example, the Moving Pictures Experts Group (MPEG) has promulgated several standards relating to digital data delivery systems. The first, known as MPEG-1 refers to ISO/IEC standards 11172 and is incorporated herein by reference. The second, known as MPEG-2, refers to ISO/IEC standards 13818 and is incorporated herein by reference. A compressed digital video system is described in the Advanced Television Systems Committee (ATSC) digital television standard document A/53, and is incorporated herein by reference.
The above-referenced standards describe data processing and manipulation techniques that are well suited to the compression and delivery of video, audio and other information using fixed or variable length digital communications systems. In particular, the above-referenced standards, and other xe2x80x9cMPEG-likexe2x80x9d standards and techniques, compress, illustratively, video information using intra-frame coding techniques (such as run-length coding, Huffman coding and the like) and inter-frame coding techniques (such as forward and backward predictive coding, motion compensation and the like). Specifically, in the case of video processing systems, MPEG and MPEG-like video processing systems are characterized by prediction-based compression encoding of video frames with or without intra- and/or inter-frame motion compensation encoding.
It is known to compress (i.e., resize) image information to reduce decoder anchor frame memory requirements or to reduce decoder processing resources in systems utilizing relatively low resolution display devices. For example, in the case of an 8xc3x978 block of DCT coefficients received by an MPEG-like decoder, it is known to consider only the 4xc3x974 lower block of DCT coefficients (i.e., truncate the: three 4xc3x974 higher order blocks), and to compute a 4xc3x974 pixel block for storage as anchor frame information.
Unfortunately, present techniques for resizing images including field-mode coded DCT coefficients do not produce adequate results, especially if the images include both frame-mode and field-mode DCT coefficients. Therefore, it is seen to be desirable to provide a method and apparatus that addresses these and other problems in the art.
The invention comprises a method and apparatus for reducing information artifacts, such as phase error artifacts, imparted to a field-mode encoded video information stream during inverse discrete cosine transform (IDCT) processing within, e.g., an MPEG-like decoder producing a resized image frame(s) from an original image frame(s). That is, the invention adapts at least a portion of the DCT coefficients used during the IDCT processing such that pixel domain correction is imparted to the resized image frame(s) during the IDCT processing of the DCT-domain information forming the original image frame(s).